METHOD OF DIFFERENTIAL PROTECTION AND DEVICE FOR DIFFERENTIAL PROTECTION Russian patent published in 2013 - IPC H02H3/28 

FIELD: electrical engineering.

SUBSTANCE: for each phase (13a, 13b, 13c) at least in two measurement points of the facility under protection (11) current value is measured, then values of differential current are determined for each phase (13a, 13b, 13c) and tripping signal is created for a certain phase (e.g. 13b) when value of differential current exceeds threshold value for this phase (e.g. 13b). At that for each phase (13a, 13b, 13c) a value of stabilised current is determined against current values and blocking signal is created for a certain phase (e.g. 13a, 13c) when respective value of stabilised current is below the preset threshold value; blocking signal suppresses tripping signal for the respective phase (e.g. 13a, 13c). Threshold value is set depending on maximum value of stabilised current and blocking signal is shaped for a certain phase only when a phase angle for this phase coincides with the maximum value of stabilised current or shifted per 180 degrees.

EFFECT: reliability improvement.

7 cl, 6 dwg